docs: demonstrate collection of mounted cycles with suspended workflows

examples/README.md

@@ -2,6 +2,7 @@
 
 | File | Purpose |
 | --- | --- |
+| [gc-lifecycle.endor](gc-lifecycle.endor) | A Page/Block/Task/await-frame cycle: hidden retained Blocks keep running, then releasing the last references permits collection despite rendering caches. |
 | [scroll-axis.endor](scroll-axis.endor) | One shared TextBlock in vertical and horizontal viewports, live axis changes and independent offsets. |
 | [windows.endor](windows.endor) | Two real native windows in one Aster VM, live shared counter state and explicit Page ownership. |
 | [tabs.endor](tabs.endor) | Three real Page tabs, shared counter state, source titles, native switching/closing and reopening through code. |

examples/gc-lifecycle.endor

@@ -0,0 +1,42 @@
+// Record ui.stats().objects, call mountCycle(), then inspect phase.value and
+// pending.value.status(). Close the tab: the referenced Block still waits.
+// releaseCycle() removes both external references; the next objects query
+// should return to the same baseline before the five-minute wait finishes.
+holder = ui.state(0)
+pending = ui.state(0)
+phase = ui.state(0)
+class CycleRect: RectBlock {
+    peer: Object
+    function wait(self: CycleRect): Unit {
+        gate = ui.sleep(self,"sleep",300000)
+        phase.set(1)
+        done = await gate
+        phase.set(2)
+        self.peer.title = "等待已结束"
+    }
+    function measure(self: CycleRect, mount: Mount, constraints: Constraints): MeasureResult {
+        observed = self.peer.title
+        return MeasureResult(180,40)
+    }
+    function paint(self: CycleRect, mount: Mount, geometry: Bounds): DisplayList {
+        observed = self.peer.title
+        return RectBlock.paint(self,mount,geometry)
+    }
+}
+function mountCycle(): Unit {
+    transient = Page()
+    transient.title = "临时引用环"
+    rect = CycleRect(180,40,8,"#3868D9",transient)
+    transient.render(rect)
+    holder.set(transient)
+    phase.set(0)
+    pending.set(ui.spawn(rect,"workflow",rect.wait))
+}
+function releaseCycle(): Unit {
+    holder.value.close()
+    holder.set(0)
+    pending.set(0)
+}
+base = Page()
+base.title = "GC 基线"
+base.render(TextBlock("关闭临时 Page 后应回收引用环",2))